Claims for Patent: 8,920,383

Summary for Patent: 8,920,383

Title:	Dose mechanism for an injection device for limiting a dose setting corresponding to the amount of medicament left
Abstract:	A mechanism for preventing setting of a dose, which exceeds the amount of a medicament in a reservoir in an injection device. The device comprises a threaded piston rod, a limiter and a driver. The three elements are arranged such that during dose setting, the limiter is moved towards an end-of-contend position, wherein dose setting is limited. The invention comprises an accumulative and a non-accumulative embodiment. The invention further relates to a mechanism for prevention ejection of a dose exceeding the set dose.
Inventor(s):	Enggaard; Christian Peter (Hillerod, DK), Moller; Claus Schmidt (Fredensborg, DK), Markussen; Tom Hede (Bagsvaerd, DK)
Assignee:	Novo Nordisk A/S (Bagsvaerd, DK)
Application Number:	11/996,409
Patent Litigation and PTAB cases:	See patent lawsuits and PTAB cases for patent 8,920,383
Patent Claims:	1. A mechanism for preventing setting of a dose which exceeds the amount of a medicament in a reservoir in an injection device, wherein a dose is set by rotating a dose setting member of a dose setting mechanism, the mechanism comprising: a piston rod having a threaded outer surface, wherein the piston rod rotates and translates axially forward during expelling of medication from the reservoir; a limiter that prevents the setting of a dose which exceeds the amount of medication in a reservoir in the device, the limiter defining a passage for the piston rod; a driver defining a passage for the limiter, the driver being coupled to the dose setting member such that rotation of the dose setting member during dose setting causes the driver to rotate; and wherein the limiter is coupled to the driver and the piston rod such that relative rotation between the driver and the piston rod during dose setting causes the limiter to move towards a stopping position. 2. A mechanism according to claim 1, further comprising a housing defining a passage for the piston rod, the passage having a threaded inner surface for engagement with the threaded outer surface of the piston rod, the housing being arranged with respect to the piston rod such that rotation of the piston rod in relation to the housing causes the piston rod to be displaced relative to the housing in a longitudinal direction. 3. A mechanism according to claim 1, further comprising a locking means for locking the piston rod against rotation in at least one direction relative to the housing. 4. A mechanism according to claim 1, wherein: the limiter has a threaded outer surface and is rotationally retained in relation to the piston rod; and the passage of the driver has a threaded inner surface for engagement with the threaded outer surface of the limiter. 5. A mechanism according to claim 1, wherein the limiter comprises a first engaging surface adapted to engage a corresponding second engaging surface of the driver. 6. A mechanism according to claim 1, wherein the limiter comprises a plurality of teeth adapted to engage corresponding teeth of the housing and/or the driver when the limiter is in the stopping position. 7. A mechanism according to claim 1, wherein: the passage of the limiter has a threaded inner surface for engagement with the threaded outer surface of the piston rod; and the driver is rotationally retained in relation to the limiter. 8. A mechanism according to claim 1, wherein the limiter comprises a first engaging surface adapted to engage a corresponding second engaging surface of the piston rod. 9. A mechanism according to claim 5, wherein the threaded outer surface of the piston rod comprises the first engaging surface and the threaded inner surface of the driver comprises the second engaging surface. 10. A mechanism according to claim 1, further comprising a ratchet mechanism interconnecting the driver and the housing. 11. A mechanism according to claim 10, wherein the ratchet mechanism comprises a first and a second part, the first part being coupled to the driver and the second part being adapted to be locked for rotation relative to the housing by means of the locking means. 12. A mechanism according to claim 10, further comprising an ejection assisting system for providing an ejection force for assisting an operator during ejection. 13. A syringe device according to claim 12, wherein the ejection assisting system comprises a spring which is strained when the dose setting member is rotated during dose setting.